A system for providing data for a manager device from an agent device using SNMPv3 (Simple Network Management Protocol version3) is known (for example, see the following Patent Reference 1). An engine ID unique to each of the agent devices is set under the SNMPv3. The manager device requests the engine ID from each of the agent devices. Each of the agent devices sends its own engine ID to the manager device by request. Then, the manager device sends a data request including the engine ID of its agent device to each of the agent devices. Each of the agent devices sends data (for example, a status or the remaining amount of consumable goods) had by its own agent device to the manager device on condition that the engine ID included in the data request matches with its own engine ID. The manager device can acquire data of each of the agent devices. In the SNMPv3, the engine ID set in the individual agent device can be used for authentication. As a result of this, security of data communication is high.    Patent Document 1: Japanese Patent Publication No. 2006-085643A
However, in this technique, it is necessary to make a response and a request of individual identification information before target data is communicated, and a communication load becomes large. Particularly, when a manager device acquires data had by each of the devices with respect to the agent devices, the communication load becomes larger as the number of agent devices is large.